Conventionally, an interface method in which an alkali aqueous solution of bisphenols and phosgene are reacted in the presence of an organic solvent, and a melting method in which bisphenols and a carbonic diester are polycondensation reacted by an ester exchange reaction are known as a production method of an aromatic polycarbonate. Above all, the melting method by the ester exchange reaction has the advantage that an aromatic polycarbonate resin can be produced inexpensively as compared with the interface method.
In the melting method, polycondensation reaction is conducted in a molten state using a molten mixture of raw materials of an aromatic dihydroxy compound and a carbonic diester in the presence of an ester exchange reaction catalyst, and after stopping the polycondensation reaction, an aromatic polycarbonate formed into pellets having a given particle size is obtained.
By the way, when a thermoplastic resin such as a polycarbonate is extrusion molded to form pellets, there was the problem that a deteriorated material generally called eye boogers is generated at an outlet of a flow path of a die, and adhered thereto, and such a deteriorated material is mixed into products, resulting in defective product. To prevent the deteriorated material form being accompanied with products, it is necessary to conduct a cleaning frequently, and this constituted a factor to decrease production capacity and to increase production loss.
In view of the above, the present applicant reported that generation of eye boogers can remarkably restrained by providing a taper at an outlet part of a flow path of a die (hereinafter sometimes referred to as a “die hole”) (see Patent Document 1).    Patent Document 1: JP-A-05-253997